Sets the physical extent size on physical volumes of this volume group.
A size suffix (k for kilobytes up to t for terabytes) is optional, megabytes
is the default if no suffix is present.
The default is 4 MB and it must be at least 1 KB and a power of 2.
Once this value has been set, it is difficult to change it without recreating
the volume group which would involve backing up and restoring data on any
logical volumes. However, if no extents need moving for the new
value to apply, it can be altered using vgchange -s.
If the volume group metadata uses lvm1 format, extents can vary in size from
8KB to 16GB and there is a limit of 65534 extents in each logical volume. The
default of 4 MB leads to a maximum logical volume size of around 256GB.
If the volume group metadata uses lvm2 format those restrictions do not apply,
but having a large number of extents will slow down the tools but have no
impact on I/O performance to the logical volume. The smallest PE is 1KB.
The 2.4 kernel has a limitation of 2TB per block device.